Method for selecting implant components

ABSTRACT

Methods of selecting or designing an implant to be used in a patient are provided. A CT scan of a patient&#39;s mouth is performed. A 3D CAD model of the patient&#39;s mouth is created utilizing data generated by the CT scan. Properties of the patient&#39;s mouth are determined based upon CT scan data and assigned to the 3D CAD model. A desired location for an implant is selected. A FEA simulation is performed on the 3D CAD model to choose an implant or to design an implant that optimizes a selected variable.

RELATED APPLICATIONS

This application is based on U.S. Provisional Application No.60/930,812, filed May 18, 2007, hereby incorporated by reference in itsentirety.

FIELD OF INVENTION

The present invention relates generally to implant systems for implantsplaced in bone. More particularly, the present invention relates torestoration components for dental implant systems and a computer modelfor selecting or developing an implant by optimizing at least onevariable utilizing finite element analysis.

BACKGROUND OF THE INVENTION

The dental restoration of a partially or wholly edentulous patient withartificial dentition is typically done in two stages. In the firststage, an incision is made through the gingiva to expose the underlyingbone. An artificial tooth root, usually a dental implant, is placed inthe jawbone for integration. The dental implant generally includes athreaded bore to receive a retaining screw holding mating componentstherein. During the first stage, the gum tissue overlying the implant issutured and heals as the osscointegration process continues.

Once the osscointegration process is complete, the second stage isinitiated. Here, the gum tissue is re-opened to expose the end of thedental implant. A healing component or healing abutment is fastened tothe exposed end of the dental implant to allow the gum tissue to healtherearound. Preferably, the gum tissue heals such that the aperturethat remains generally approximates the size and contour of the aperturethat existed around the natural tooth that is being replaced. Toaccomplish this, the healing abutment attached to the exposed end of thedental implant has the same general contour as the gingival portion ofthe natural tooth being replaced.

During the typical second stage of dental restoration, the healingabutment is removed and an impression coping is fitted onto the exposedend of the implant. This allows an impression of the specific region ofthe patient's mouth to be taken so that an artificial tooth isaccurately constructed. Thus, in typical dental implant systems, thehealing component and the impression coping are two physically separatecomponents. Preferably, the impression coping has the same gingivaldimensions as the healing component so that there is no gap between theimpression coping and the wall of the gum tissue defining the aperture.Otherwise, a less than accurate impression of the condition of thepatient's mouth is made. The impression coping may be a “pick-up” typeimpression coping or a “transfer” type impression coping, both known inthe art. After these processes, a dental laboratory creates a prosthesisto be permanently secured to the dental implant from the impression thatwas made.

More recently, single stage restoration have become more common, wherean implant is placed in the patients mouth and a prosthesis is placed onthis implant during the same procedure. Such a procedure typicallyreduces the number of visits a patient must make to a clinician,however, additional complications may occur in a patient during singlestage restoration if an implant lacks proper initial stability. One wayto help predict initial implant stability involves using finite elementanalysis (“FEA”) to attempt to predict effects of placing the implantinto bone. These effects may include stress levels within the implant,stress levels in bone surrounding the implant, initial implantstability, torque required to seat an implant and many other factors.However, a real-time FEA simulation of the placement of an implant intobone has not been performed to date. Rather FEA simulations have onlyfocused on the implant after it has already been placed into bone. Thus,a need exists for a method to accurately predict effects of placing animplant into bone.

SUMMARY OF THE INVENTION

According to one process, a method of selecting an implant to be used ina patient is provided that performs a CT scan of a patient's mouth. Themethod creates a 3D CAD model of the patient's mouth utilizing datagenerated by the CT scan. Properties of the patient's mouth aredetermined based upon data generated by the CT scan. The determinedproperties of the patient's mouth are assigned to the 3D CAD model. Themethod selects a desired location for the implant. The implant to beplaced into the patient is selected. The method performs an FEAsimulation of the selected implant being installed in the patient'smouth with the 3D CAD model. The method confirms the implant chosen bythe act of selecting is clinically appropriate based upon the results ofthe FEA simulation of the 3D CAD model.

According to another process, a method of selecting an implant to beused in a patient is provided that performs a CT scan of the patient'smouth. A 3D CAD model of the patient's mouth is created utilizing datagenerated by the CT scan. The method determines properties of thepatient's mouth based upon data generated by the CT scan. The determinedproperties of the patient's mouth are assigned to the 3D CAD model. Themethod selects a desired location for the implant. At least one variableto be optimized by a FEA simulation is assigned. The method performs anFEA simulation on the 3D CAD model to optimize the assigned variable.The method choosing the implant from a plurality of implants to use inthe patient based upon results from the act of performing the FEAsimulation.

According to a further process a method of designing an implant to beused in a patient is provided that performs a CT scan of the patient'smouth. The method creates a 3D CAD model of the patient's mouthutilizing data generated by the CT scan. Properties of the patient'smouth are determined based upon data generated by the CT scan. Thedetermined properties of the patient's mouth are assigned to the 3D CADmodel. The method selects a desired location for the implant. At leastone variable to be optimized by a FEA simulation is assigned. The methodperforms a FEA simulation on the 3D CAD model to optimize the assignedvariable. The implant to use in the patient is designed based uponresults from the act of performing the FEA simulation.

According to yet another process, a method of verifying a FEA simulationused to select an implant is provided that creates a 3D CAD model of anactual calibration sample. Properties of the actual calibration sampleare assigned to the 3D CAD model. The method performs an FEA simulationof placing the implant into the calibration sample on the 3D CAD modelto generate FEA simulation data. An actual implant is placed into theactual calibration sample. The method collects measured data during theplacement of the actual implant into the actual calibration sample. Themeasured data gathered during the act of collecting measured data iscompared with the FEA simulation data generated by the act of performingthe FEA simulation. The method ascertains whether the FEA simulationdata accurately predicts the measured data. The method modifies FEAsimulation variables if the act of ascertaining determines the FEAsimulation does not accurately predict the measured data.

According to yet a further process, a method of selecting an implant tobe used in a patient performs a CT scan of a region of the patient'sbody to contain the implant. A 3D CAD model of the region of thepatient's body is created utilizing data generated by the CT scan.Properties of the region of the patient's body are determined based upondata generated by the CT scan. The method assigns the determinedproperties of the region of the patient's body to the 3D CAD model. Adesired location for the implant is selected. The method selects theimplant to be placed into the patient. An FEA simulation is performed ofthe selected implant being installed in the region of the patient's bodywith the 3D CAD model. The method confirms the implant chosen by the actof selecting is clinically appropriate based upon the results of the FEAsimulation of the 3D CAD model.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a method according to one process forselecting a dental implant by utilizing a Finite Element Analysis(“FEA”) simulation:

FIG. 2 is a block diagram of a method according to another process forselecting a dental implant by utilizing a FEA simulation;

FIG. 3 is a block diagram of a method according to a further process fordesigning a dental implant by utilizing a FEA simulation;

FIG. 4 is a block diagram of a method according to one process forverifying a FEA simulation.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof have been shown by wayof example in the drawings and will herein be described in detail. Itshould be understood, however, that it is not intended to limit theinvention to the particular forms disclosed but, on the contrary, theintention is to cover all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by theappended claims.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

As shown in FIG. 1 a method 10 is shown to determine initial implantstability. As shown in block 12, a CT scan is performed on a patient. Itis contemplated that various types of CT scans may be performed, such asConcentric CT scans or Cone-Beam CT scans. The CT scan produces datathat may be used in forming a 3D CAD model of a patient's mouth within aCAD system as depicted in block 14. The CT scan allows a determinationto be made regarding the type of bone found in the patient's mandible ormaxilla where the implant is to be placed.

For example, the CT scan allows a practitioner to determine that Type Ibone is present, a bone type that has almost all cortical bone tissue.Similarly, the CT scan may reveal that Type II, Type III, or Type IVbone is present at additional different planned implant locations. Thevarious bone types have properties associated therewith, such as Type Ibone being harder than Type IV bone. An implant being placed in Type Ibone requires additional torque to seat the implant than an implantbeing placed in Type IV bone.

It is additionally contemplated that other technologies than CT scanningmay be utilized to generate data used to form the 3D CAD model, such asultrasonic scanning, MRI, or other scanning techniques.

Once the type, or types, of bone that implants will be placed in isdetermined, material properties for the bone may be assigned to the 3DCAD model of the patient's mouth, as shown in block 16.

The 3D CAD model of the patient's mouth allows a practitioner todetermine locations to place the implants to be utilized, and alsoallows the practitioner to select particular implants to use on thepatient. First, by analyzing the patient's particular anatomicalstructure, the practitioner determines desired locations for implants atblock 18. Based on the patient's anatomical structure at the desiredlocations, a practitioner selects an implant to be placed within thepatient at block 20. As the general ranges for material properties forType I-Type IV bone are known, the 3D CAD model of the bones of thepatient are assigned material properties at block 22. The assigning ofmaterial properties may be performed automatically by software based onthe results of the CT scan, or a practitioner may analyze the CT scanand assign material properties to the 3D CAD model of the patient basedon what is shown on the CT scan. Based on output from CT scan, such asthe number of Hounstield's units obtained from the CT scan, a bone typemay be obtained.

The CAD system contains a library of dental implants and otherrestorative components that a practitioner may choose from whendeveloping a treatment plan for a patient. As shown at block 24, thepractitioner selects a proposed implant to use within a first implantsite of the patient within the CAD system. The CAD system contains alibrary of dental implants, so that 3D models exist of the variousimplants that a practitioner may select. The selection of a proposedimplant also causes the CAD system to create an osteotomy for theselected implant at the first implant site of the 3D CAD model.

As depicted in block 26, once the practitioner has selected a proposedimplant, a finite element analysis (“FEA”) simulation is preformed. TheFEA simulation may evaluate placing the implant into a patient's bone,the implant and bone immediately after placement of the implant, andfurther may analyze the implant and bone after oseointegration occurs.Thus, the FEA simulation analyzes the characteristics and conditions theimplant and the bone as the implant is being placed into the bone, notjust following the placement of the implant.

The FEA simulation of the implant placement analyzes the torquenecessary to seat the implant into the bone. Based on the bone typepresent in the area around the implant site, as well as thecharacteristics of the implant and characteristic of the osteotomy, theamount of torque required to drive the implant into the bone isdetermined using the FEA simulation. After the simulation has determinedthe torque required to seat the implant within the bone, initial implantstability is analyzed. Knowing the amount of torque required to seat theimplant is important, as using more torque than required to obtain aneeded level of initial implant stability can generate more frictionbetween the implant and the bone, which generates heat that can damagebone cells near the implant.

Initial implant stability is a measure of the stiffness of theconnection between the bone and the dental implant, prior toosseointegration occurring. Initial implant stability can be used todetermine how likely it is that the implant may loosen prior toosscointegration occurring. The higher the initial implant stability,the less likely the implant is to come loose. Factors that may influenceinitial implant stability, and that can be accounted for in the FEAsimulation, include implant geometry, such as the thread design andimplant size, bone type, and osteotomy properties, such as osteotomygeometry, whether the osteotomy has a counter sink, and whether theosteotomy is tapped.

Further, the FEA simulation may be used to calculate a resonantfrequency of the implant and bone assembly, at the time of implantation.A resonant frequency analysis (“RFA”) allows a practitioner to track theosseointegration of the implant. As the implant is integrated into thebone, the resonant frequency changes, indicating to the practitioner howosseointegration is progressing.

The FEA simulation further may be used to analyze the stress and straingenerated as the implant is placed in to the osteotomy. This analysiscan be used to evaluate the stress and strain at the interface of thebone and the implant, as well as the stress and strain within thepatient's bone. Thus, the FEA simulation allows a practitioner todetermine the potential stress and strain that will exist within thepatient as the implant is placed into the bone.

Thus, the FEA simulation allows a practitioner to evaluate many factorsof a selected implant in a 3D virtual environment, prior to performingany surgical procedures on a patient. Thus, a practitioner may select animplant, virtually place the implant into the 3D model of the patient'sbone, and perform an FEA simulation on the implant and the bone as theimplant is being placed into the 3D model of the patient's bone.

From the FEA simulation, a practitioner may determine, as shown in block28, whether the selected implant offers necessary initial implantstability without requiring too high a level of torque being needed toplace the implant into the patient's bone and without placing too muchstress or strain on the bone. If the practitioner determines that theFEA simulation indicates that the selected implant meets the patient'sclinical needs and offers appropriate initial implant stability withoutproducing too much stress or strain within the bone or at the bone andimplant interface, the practitioner has verified that an acceptableimplant has been selected.

If the selected implant is determined to not meet the patient's clinicalneeds, the practitioner selects a different implant, and repeats theprocess as shown in blocks 20-28 until an acceptable implant is found.

Once an acceptable implant is found, as shown in block 30, it isdetermined if there are any additional implant locations that need to beanalyzed. If there are additional implant locations, the practitionerrepeats the process shown in blocks 18-28 until there are no additionalimplant locations.

Once every desired implant location has been analyzed and an appropriateimplant for each proposed location found, the FEA simulation may beended.

It is contemplated that the FEA simulation may allow one or more of theproperties to be optimized. For example, initial implant stability maybe optimized, such that the selected implant allows immediate loading ina manner that will be less likely to cause the implant to come looseprior to osseointegration. Similarly, an implant may be selected thatmaximizes the initial implant stability relative to a given maximumtorque required to install an implant.

Turning now to FIG. 2, a method 100 is shown that depicts a similarmethod to the method 10 depicted in FIG. 1, expect the method 100 ofFIG. 2 uses software to optimize the implant selection based on aselected criteria or criterion.

As shown in block 112, a CT scan is performed on a patient that is usedin block 114 to create a 3D CAD model of the patient's mouth. Based onthe CT scan, properties of the patient's bone may be determined, asshown in block 116. It is contemplated that the properties of thepatient's bone may be determined by selecting the types of bone in apatient's mouth, and assigning properties to regions of the 3D CAD modelbased upon typical material properties for that type of bone as shown inblock 118. Alternatively, the CT scan may be used to determine bonedensity such that a magnitude of bone density is assigned variousregions within the 3D CAD model based upon the CT scan.

Once the 3D CAD model has been assigned properties based upon the CTscan, the practitioner determines the desired locations for implantplacement, as shown at block 120. Next, as shown in block 122, thepractitioner determines at least one variable to optimize utilizing aFEA simulation. The variable to be optimized may be, for example, theinitial implant stability, the amount of torque to install an implant,an acceptable amount of stress and strain within the bone around theimplant, some other variable, or some combination of variables. Anexample of a combination of variables would be to optimize the initialimplant stability for a low torque level required to seat an implant.

After the variable, or variables, to be optimized is selected, a FEAsimulation of implant placement is performed at block 124. The FEAsimulation may evaluate a plurality of implants contained in a libraryof the 3D CAD system. The FEA simulation produces a result at block 126that informs a practitioner of the implant that optimizes the result forthe variable, or variables, the practitioner had selected. For example,if a practitioner had chosen to maximize initial implant stability whileminimizing placement torque, the FEA simulation would be performed on avariety of implants, and the FEA simulation would inform thepractitioner of the particular implant that best meets the selectedcriterion. Once the implant for a first desired location has beenselected, it is determined at block 128 if there are any additionalimplants required by the patient. If additional implants are required,the method returns to step 120 for the next implant. If there are noadditional implants, the FEA simulation is ended, as shown in block 130.

It is contemplated according to another method that the practitioner mayconstrain the results given by the FEA simulation as shown in FIG. 2.For example, the practitioner may specify a diameter for the implant,and then the FEA simulation will be limited to optimizing the criterionselected only for implants of the chosen diameter. Additional examplesof variable constraints the practitioner may place on the FEA simulationinclude, but are not limited to, implant length, implant thread design,osteotomy profile, whether the osteotomy has a countersink, and whetherthe osteotomy is tapped.

As shown in FIG. 3, a further method 200 is shown in which a custompatient specific implant is designed based upon an FEA simulation.Similar to the methods previously described, a CT scan of a patient'smouth is taken at block 212. From the CT scan, a 3D CAD model of thepatient's mouth is created, as depicted at block 214. As depicted atblock 216, properties of the patient's bone are determined from the CTscan, such as bone type, or bone density. Once the properties of thepatient's mouth are determined, the properties are assigned to 3D CADmodel of the patient's mouth at block 218.

At block 220 of FIG. 3, the practitioner then selects desired locationsfor at least one implant. The practitioner at block 222 selects at leastone variable to optimize using an FEA simulation, such as, for example,creating a high level of initial implant stability with a low level oftorque required to seat the implant.

An FEA simulation is performed on the 3D CAD model to determineimplant-design variables at step 224. Based upon the implant-designvariables determined by the FEA simulation, a custom implant is designedfor the patient that optimizes the at least one variable previouslyselected by the practitioner, as shown at block 226. A 3D CAD model ofthe custom implant is created at block 228 that may be used to machine acustom implant. The method determines at block 230 if there is anadditional implant required by the patient. If there is, the methodreturns to block 220 if not, the FEA simulation is ended as shown atblock 232.

It is contemplated according to some processes that a limited number ofimplant design variables may be modified to create a custom implant fora patient. Implant variables that may be modified include, but are notlimited to, implant diameter, implant length, implant material, implantsurface preparation, and implant thread design including thread type,thread width, diameter, and the thread pitch.

While an FEA simulation is a valuable tool for selecting or designing aproper implant for a patient, the FEA simulation must be verified bycomparing an FEA simulation with measured data collected when placing animplant into a sample, as shown by method 300 in FIG. 4. FIG. 4illustrates the manner in which the FEA modeling analysis is verified.

As shown at block 310, a CT scan is performed on a calibration sample.Actual material properties of the calibration sample are known. Datagenerated by the CT scan of the calibration sample is used to form a 3DCAD model of the calibration sample at block 312. Next, properties ofthe calibration sample are determined at block 314 and assigned to the3D CAD model at block 316. A desired location for placing the implantwithin the calibration sample is selected at block 318. Block 320depicts a FEA simulation being performed on the 3D CAD model.

As shown at block 322, an actual implant is placed into the calibrationsample. The implant is placed into the calibration sample using a testfixture that measures data during the placement of the implant into thecalibration sample as shown at block 324. Examples of data that may becollected include the torque required to place the implant, the stressand strain levels of the implant, and the stress and strain level of thecalibration sample near the implant. Once the measured data is obtained,the FEA simulation results are compared to the measured data, as shownat block 326. Next it is determined whether the FEA simulation resultcompares favorably with the measured data, as shown in block 328. If theFEA simulation does not accurately predict the measured data, FEAsimulation variables are adjusted at block 330. Non-limiting examples ofvariables that may be adjusted include material properties, such as themodulus of elasticity of the bone, the yield strength of the bone orimplant, shear strength of the bone or implant, mechanical properties,failure criteria, such as why the implant or bone failed, and failureresponse, such as what happened to the bone after failure. Afteradjusting the FEA simulation variables, the FEA simulation is performedagain using the adjusted variables as shown at block 332. The adjustedFEA simulation results are then again compared with the measured data,and this process repeats until the FEA simulation results closely trackthe measured data. Once the FEA simulation is determined to accuratelypredict the measured data, the FEA simulation is considered to beproperly calibrated, as shown at block 334.

Once the method 300 depicted in FIG. 4 is completed, one of the previousanalysis methods shown in FIGS. 1-3 may be performed with confidencethat the FEA simulation model produces results that accurately predictthe forces and stresses present during the placement of the implant.

While the above methods have been described using CT scanning togenerate data to form a 3D CAD model, it is contemplated that othermethods may be used to gather this data. For example, an X-ray may beused in place of CT scan.

While the above embodiments have related to dental implants, it iscontemplated that the above described methods may be utilized on otherregions of a patient's body with other types of non-dental implants,such as orthopedic implants.

While particular embodiments and applications of the present inventionhave been illustrated and described, it is to be understood that theinvention is not limited to the precise construction and compositionsdisclosed herein and that various modifications, changes, and variationsmay be apparent from the foregoing descriptions without departing fromthe spirit and scope of the invention as defined in the appended claims.

What is claimed is:
 1. A method of selecting an implant to be used in apatient comprising the acts of: performing a CT scan of the patient'smouth; creating a 3D CAD model of the patient's mouth utilizing datagenerated by the CT scan; determining properties of the patient's mouthbased upon data generated by the CT scan; assigning the determinedproperties of the patient's mouth to the 3D CAD model; selecting adesired location for the implant; selecting the implant to be placedinto the patient; performing an FEA simulation of the selected implantbeing installed in the patient's mouth with the 3D CAD model; andconfirming the implant chosen by the act of selecting is clinicallyappropriate based upon the results of the FEA simulation of the 3D CADmodel.
 2. The method of claim 1, wherein the act of determiningproperties determines a type of bone present in the patient's jaw. 3.The method of claim 1, wherein the act of determining propertiesdetermines a magnitude of bone density of the patient's jaw.
 4. Themethod of claim 1, wherein the act of selecting the implant selects a 3DCAD model of the implant from a CAD library and adds the implant to the3D CAD model at the desired location.
 5. The method of claim 1, whereinthe act of performing an FEA simulation is a real-time simulation ofplacing the implant into the patient's bone.
 6. The method of claim 1,wherein the act of confirming is based upon optimizing initial implantstability while utilizing a given torque level to seat the implant inthe bone.
 7. The method of claim 1, wherein the act of confirming isbased upon verifying that a maximum stress level is not surpassed in thebone surrounding the implant.
 8. A method of selecting an implant to beused in a patient comprising the acts of: performing a CT scan of thepatient's mouth; creating a 3D CAD model of the patient's mouthutilizing data generated by the CT scan; determining properties of thepatient's mouth based upon data generated by the CT scan; assigning thedetermined properties of the patient's mouth to the 3D CAD model;selecting a desired location for the implant; assigning at least onevariable to be optimized by a FEA simulation; performing an FEAsimulation on the 3D CAD model to optimize the assigned variable; andchoosing the implant from a plurality of implants to use in the patientbased upon results from the act of performing the FEA simulation.
 9. Themethod of claim 8, wherein the act of determining properties determinesa type of bone present in the patient's jaw.
 10. The method of claim 8,wherein the act of determining properties determines a magnitude of bonedensity of the patient's jaw.
 11. The method of claim 8, wherein the actof performing an FEA simulation is a real-time simulation of placing theimplant into the patient's bone.
 12. The method of claim 8, wherein theact of assigning the at least one variable to optimize assigns initialimplant stability relative to a given torque level to seat the implantin the bone as the variable to optimize.
 13. The method of claim 8,wherein the act of assigning the at least one variable to optimizeassigns a maximum stress level not to be surpassed in the bonesurrounding the implant.
 14. The method of claim 8, wherein the act ofperforming an FEA simulation occurs on a plurality of possible implantscontained in a library of the 3D CAD system to optimize the assignedvariable.
 15. A method of designing an implant to be used in a patientcomprising the acts of: performing a CT scan of the patient's mouth;creating a 3D CAD model of the patient's mouth utilizing data generatedby the CT scan; determining properties of the patient's mouth based upondata generated by the CT scan; assigning the determined properties ofthe patient's mouth to the 3D CAD model; selecting a desired locationfor the implant; assigning at least one variable to be optimized by aFEA simulation; performing a FEA simulation on the 3D CAD model tooptimize the assigned variable; and designing the implant to use in thepatient based upon results from the act of performing the FEAsimulation.
 16. The method of claim 15, wherein the act of determiningproperties determines a type of bone present in the patient's jaw. 17.The method of claim 15, wherein the act of determining propertiesdetermines a magnitude of bone density of the patient's jaw.
 18. Themethod of claim 15, wherein the act of performing an FEA simulation is areal-time simulation of placing the implant into the patient's bone. 19.The method of claim 15, wherein the act of designing the implantincludes determining at least one implant dimension from the FEAsimulation performed.
 20. The method of claim 19, wherein the implantdimension determined is the implant diameter, implant length, or implantthread type.